Field of the Invention
The present invention relates to an optical unit, an optical apparatus using the same, a light source apparatus, and a projection display apparatus. The present invention particularly relates to a light source apparatus using a solid light source such as a semiconductor laser as a light source.
Description of the Related Art
In recent years, there has been developed a projector which irradiates a fluorescent body with light fluxes emitted from high-output laser diodes (LD) as excitation light and uses wavelength-converted fluorescent light.
It is presumed that many LDs are arranged and used to realize high luminescence with in a projector. However, light output of the LDs is reduced at a higher temperature, and thus when the LDs are densely arranged giving a priority to downsizing of the projector, the LDs give heat to each other and the light output of the LDs is reduced, which deteriorates brightness of a projected image.
For that reason, it is required that the LDs are arranged at wider intervals so that mutual heat effect is reduced as much as possible. However, when the arrangement intervals become wider, light fluxes exiting the group of LDs become thicker and a size of a subsequent optical element is also increased, which is not desirable in terms of cost and weight.
In light of the above problem, a technique for thinning light fluxes exiting a group of LDs as much as possible is described in Japanese Patent Application Laid-Open No. 2011-65770 and United States Patent Publication Application No. 2014/0111775.
Japanese Patent Application Laid-Open No. 2011-65770 discusses a technique in which a plurality of planar mirrors is provided in a traveling direction of light fluxes from a plurality of LDs and the angle of each of the planar mirrors is adjusted to condense the light on a fluorescent body.
United States Patent Publication Application No. 2014/0111775 discusses a technique in which one paraboloid mirror is provided in a traveling direction of light fluxes from a plurality of LDs and the light fluxes from the paraboloid mirror are reflected on a mirror to be condensed on a fluorescent body.
By employing the techniques discussed in Japanese Patent Application Laid-Open No. 2011-65770 and United States Patent Publication Application No. 2014/0111775, an increase in a size of the optical element can be prevented.
However, in the structure described in Japanese Patent Application Laid-Open No. 2011-65770, the reflective surfaces of the mirrors are planar and thus it is difficult to condense parallel light fluxes reflected on the mirrors to a small area on the fluorescent body.
If a condensing spot on the fluorescent body is large, parallelism of light lowers when the light is incident on the subsequent optical system, and light utilization efficiency can be deteriorated.
On the other hand, in the structure described in United States Patent Publication Application No. 2014/0111775, since a paraboloid mirror is used, convergent light fluxes from the paraboloid mirror are condensed on a small area on the fluorescent body, which prevents the deterioration in light utilization efficiency.
However, with the structure described in United States Patent Publication Application No. 2014/0111775, when the number of LDs increases to obtain higher luminance, the paraboloid mirror becomes wider in area and deeper, which may increase the size of the light source apparatus.